MicroPython Forum (Archive)

Posted: **Thu Jun 02, 2022 3:12 am**

After referring to @dhylands 'example at https://github.com/dhylands/upy-example ... ncoder2.py, I found the prescaler setting does matter and prescaler=0 won't work whatsoever whereas prescaler=1 really works. Why is that?
Additionally, although prescaler=1 makes the encoder mode work, it indeed counts in opposite direction.
For example, if period set to 10000, the counting follows 0->10000->9999->9998 ... ->0->10000->9999, etc.
After trying out all the tweaks that I can imagine, the counting behavior does not change at all?
Is it a bug or something I obviously overlooked?
P.S. I use MicroPython v1.18 on 2022-01-17; PYBv1.1 with STM32F405RG

Posted: **Thu Jun 02, 2022 5:56 am**

If you swap the wires of the encoder, the counting direction will change.

Posted: **Thu Jun 02, 2022 6:09 am**

Roberthh wrote: ↑
Thu Jun 02, 2022 5:56 am
If you swap the wires of the encoder, the counting direction will change.

Yes, it's true. But why is that?
I tried

Code: Select all

        x_cnt = Pin(Pin.cpu.A1, Pin.AF_PP, pull=Pin.PULL_DOWN, af=Pin.AF2_TIM5)
        x_timer = Timer(5, prescaler=1, period=0x3fffffff)
        x_channel = x_timer.channel(1, Timer.ENC_B)  # The channel number is ignored when setting the encoder mode

        y_cnt = Pin(Pin.cpu.B6, Pin.AF_PP, pull=Pin.PULL_DOWN, af=Pin.AF2_TIM4)
        y_timer = Timer(4, prescaler=1, period=0xffff)
        y_channel = y_timer.channel(1, Timer.ENC_A)

Both counting up by default. What is so special with?

Code: Select all

        z_cnt = Pin('X1', Pin.AF_OD, pull=Pin.PULL_DOWN, af=Pin.AF1_TIM2)
        z_timer = Timer(2, prescaler=1, period=0x3fffffff)
        z_channel = z_timer.channel(1, Timer.ENC_A)

This one counts down by default.

Posted: **Thu Jun 02, 2022 7:28 am**

I think I've found why.
You need to have the other pin-pair in fixed state to make sure the counting direction is determined.
If so, the other pin-pair needs to be reserved instead of being used for other purpose as it could bring up random state when the counting starts.

MicroPython Forum (Archive)

Why the encoder counting down?

Why the encoder counting down?

Re: Why the encoder counting down?

Re: Why the encoder counting down?

Re: Why the encoder counting down?